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1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2019 Facebook */
3
4#include <linux/bpf.h>
5#include <linux/bpf_verifier.h>
6#include <linux/btf.h>
7#include <linux/filter.h>
8#include <linux/slab.h>
9#include <linux/numa.h>
10#include <linux/seq_file.h>
11#include <linux/refcount.h>
12#include <linux/mutex.h>
13#include <linux/btf_ids.h>
14#include <linux/rcupdate_wait.h>
15
16enum bpf_struct_ops_state {
17 BPF_STRUCT_OPS_STATE_INIT,
18 BPF_STRUCT_OPS_STATE_INUSE,
19 BPF_STRUCT_OPS_STATE_TOBEFREE,
20 BPF_STRUCT_OPS_STATE_READY,
21};
22
23#define BPF_STRUCT_OPS_COMMON_VALUE \
24 refcount_t refcnt; \
25 enum bpf_struct_ops_state state
26
27struct bpf_struct_ops_value {
28 BPF_STRUCT_OPS_COMMON_VALUE;
29 char data[] ____cacheline_aligned_in_smp;
30};
31
32struct bpf_struct_ops_map {
33 struct bpf_map map;
34 struct rcu_head rcu;
35 const struct bpf_struct_ops *st_ops;
36 /* protect map_update */
37 struct mutex lock;
38 /* link has all the bpf_links that is populated
39 * to the func ptr of the kernel's struct
40 * (in kvalue.data).
41 */
42 struct bpf_link **links;
43 /* image is a page that has all the trampolines
44 * that stores the func args before calling the bpf_prog.
45 * A PAGE_SIZE "image" is enough to store all trampoline for
46 * "links[]".
47 */
48 void *image;
49 /* uvalue->data stores the kernel struct
50 * (e.g. tcp_congestion_ops) that is more useful
51 * to userspace than the kvalue. For example,
52 * the bpf_prog's id is stored instead of the kernel
53 * address of a func ptr.
54 */
55 struct bpf_struct_ops_value *uvalue;
56 /* kvalue.data stores the actual kernel's struct
57 * (e.g. tcp_congestion_ops) that will be
58 * registered to the kernel subsystem.
59 */
60 struct bpf_struct_ops_value kvalue;
61};
62
63struct bpf_struct_ops_link {
64 struct bpf_link link;
65 struct bpf_map __rcu *map;
66};
67
68static DEFINE_MUTEX(update_mutex);
69
70#define VALUE_PREFIX "bpf_struct_ops_"
71#define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
72
73/* bpf_struct_ops_##_name (e.g. bpf_struct_ops_tcp_congestion_ops) is
74 * the map's value exposed to the userspace and its btf-type-id is
75 * stored at the map->btf_vmlinux_value_type_id.
76 *
77 */
78#define BPF_STRUCT_OPS_TYPE(_name) \
79extern struct bpf_struct_ops bpf_##_name; \
80 \
81struct bpf_struct_ops_##_name { \
82 BPF_STRUCT_OPS_COMMON_VALUE; \
83 struct _name data ____cacheline_aligned_in_smp; \
84};
85#include "bpf_struct_ops_types.h"
86#undef BPF_STRUCT_OPS_TYPE
87
88enum {
89#define BPF_STRUCT_OPS_TYPE(_name) BPF_STRUCT_OPS_TYPE_##_name,
90#include "bpf_struct_ops_types.h"
91#undef BPF_STRUCT_OPS_TYPE
92 __NR_BPF_STRUCT_OPS_TYPE,
93};
94
95static struct bpf_struct_ops * const bpf_struct_ops[] = {
96#define BPF_STRUCT_OPS_TYPE(_name) \
97 [BPF_STRUCT_OPS_TYPE_##_name] = &bpf_##_name,
98#include "bpf_struct_ops_types.h"
99#undef BPF_STRUCT_OPS_TYPE
100};
101
102const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
103};
104
105const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
106#ifdef CONFIG_NET
107 .test_run = bpf_struct_ops_test_run,
108#endif
109};
110
111static const struct btf_type *module_type;
112
113void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
114{
115 s32 type_id, value_id, module_id;
116 const struct btf_member *member;
117 struct bpf_struct_ops *st_ops;
118 const struct btf_type *t;
119 char value_name[128];
120 const char *mname;
121 u32 i, j;
122
123 /* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
124#define BPF_STRUCT_OPS_TYPE(_name) BTF_TYPE_EMIT(struct bpf_struct_ops_##_name);
125#include "bpf_struct_ops_types.h"
126#undef BPF_STRUCT_OPS_TYPE
127
128 module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
129 if (module_id < 0) {
130 pr_warn("Cannot find struct module in btf_vmlinux\n");
131 return;
132 }
133 module_type = btf_type_by_id(btf, module_id);
134
135 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
136 st_ops = bpf_struct_ops[i];
137
138 if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
139 sizeof(value_name)) {
140 pr_warn("struct_ops name %s is too long\n",
141 st_ops->name);
142 continue;
143 }
144 sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
145
146 value_id = btf_find_by_name_kind(btf, value_name,
147 BTF_KIND_STRUCT);
148 if (value_id < 0) {
149 pr_warn("Cannot find struct %s in btf_vmlinux\n",
150 value_name);
151 continue;
152 }
153
154 type_id = btf_find_by_name_kind(btf, st_ops->name,
155 BTF_KIND_STRUCT);
156 if (type_id < 0) {
157 pr_warn("Cannot find struct %s in btf_vmlinux\n",
158 st_ops->name);
159 continue;
160 }
161 t = btf_type_by_id(btf, type_id);
162 if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
163 pr_warn("Cannot support #%u members in struct %s\n",
164 btf_type_vlen(t), st_ops->name);
165 continue;
166 }
167
168 for_each_member(j, t, member) {
169 const struct btf_type *func_proto;
170
171 mname = btf_name_by_offset(btf, member->name_off);
172 if (!*mname) {
173 pr_warn("anon member in struct %s is not supported\n",
174 st_ops->name);
175 break;
176 }
177
178 if (__btf_member_bitfield_size(t, member)) {
179 pr_warn("bit field member %s in struct %s is not supported\n",
180 mname, st_ops->name);
181 break;
182 }
183
184 func_proto = btf_type_resolve_func_ptr(btf,
185 member->type,
186 NULL);
187 if (func_proto &&
188 btf_distill_func_proto(log, btf,
189 func_proto, mname,
190 &st_ops->func_models[j])) {
191 pr_warn("Error in parsing func ptr %s in struct %s\n",
192 mname, st_ops->name);
193 break;
194 }
195 }
196
197 if (j == btf_type_vlen(t)) {
198 if (st_ops->init(btf)) {
199 pr_warn("Error in init bpf_struct_ops %s\n",
200 st_ops->name);
201 } else {
202 st_ops->type_id = type_id;
203 st_ops->type = t;
204 st_ops->value_id = value_id;
205 st_ops->value_type = btf_type_by_id(btf,
206 value_id);
207 }
208 }
209 }
210}
211
212extern struct btf *btf_vmlinux;
213
214static const struct bpf_struct_ops *
215bpf_struct_ops_find_value(u32 value_id)
216{
217 unsigned int i;
218
219 if (!value_id || !btf_vmlinux)
220 return NULL;
221
222 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
223 if (bpf_struct_ops[i]->value_id == value_id)
224 return bpf_struct_ops[i];
225 }
226
227 return NULL;
228}
229
230const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
231{
232 unsigned int i;
233
234 if (!type_id || !btf_vmlinux)
235 return NULL;
236
237 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
238 if (bpf_struct_ops[i]->type_id == type_id)
239 return bpf_struct_ops[i];
240 }
241
242 return NULL;
243}
244
245static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
246 void *next_key)
247{
248 if (key && *(u32 *)key == 0)
249 return -ENOENT;
250
251 *(u32 *)next_key = 0;
252 return 0;
253}
254
255int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
256 void *value)
257{
258 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
259 struct bpf_struct_ops_value *uvalue, *kvalue;
260 enum bpf_struct_ops_state state;
261 s64 refcnt;
262
263 if (unlikely(*(u32 *)key != 0))
264 return -ENOENT;
265
266 kvalue = &st_map->kvalue;
267 /* Pair with smp_store_release() during map_update */
268 state = smp_load_acquire(&kvalue->state);
269 if (state == BPF_STRUCT_OPS_STATE_INIT) {
270 memset(value, 0, map->value_size);
271 return 0;
272 }
273
274 /* No lock is needed. state and refcnt do not need
275 * to be updated together under atomic context.
276 */
277 uvalue = value;
278 memcpy(uvalue, st_map->uvalue, map->value_size);
279 uvalue->state = state;
280
281 /* This value offers the user space a general estimate of how
282 * many sockets are still utilizing this struct_ops for TCP
283 * congestion control. The number might not be exact, but it
284 * should sufficiently meet our present goals.
285 */
286 refcnt = atomic64_read(&map->refcnt) - atomic64_read(&map->usercnt);
287 refcount_set(&uvalue->refcnt, max_t(s64, refcnt, 0));
288
289 return 0;
290}
291
292static void *bpf_struct_ops_map_lookup_elem(struct bpf_map *map, void *key)
293{
294 return ERR_PTR(-EINVAL);
295}
296
297static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
298{
299 const struct btf_type *t = st_map->st_ops->type;
300 u32 i;
301
302 for (i = 0; i < btf_type_vlen(t); i++) {
303 if (st_map->links[i]) {
304 bpf_link_put(st_map->links[i]);
305 st_map->links[i] = NULL;
306 }
307 }
308}
309
310static int check_zero_holes(const struct btf_type *t, void *data)
311{
312 const struct btf_member *member;
313 u32 i, moff, msize, prev_mend = 0;
314 const struct btf_type *mtype;
315
316 for_each_member(i, t, member) {
317 moff = __btf_member_bit_offset(t, member) / 8;
318 if (moff > prev_mend &&
319 memchr_inv(data + prev_mend, 0, moff - prev_mend))
320 return -EINVAL;
321
322 mtype = btf_type_by_id(btf_vmlinux, member->type);
323 mtype = btf_resolve_size(btf_vmlinux, mtype, &msize);
324 if (IS_ERR(mtype))
325 return PTR_ERR(mtype);
326 prev_mend = moff + msize;
327 }
328
329 if (t->size > prev_mend &&
330 memchr_inv(data + prev_mend, 0, t->size - prev_mend))
331 return -EINVAL;
332
333 return 0;
334}
335
336static void bpf_struct_ops_link_release(struct bpf_link *link)
337{
338}
339
340static void bpf_struct_ops_link_dealloc(struct bpf_link *link)
341{
342 struct bpf_tramp_link *tlink = container_of(link, struct bpf_tramp_link, link);
343
344 kfree(tlink);
345}
346
347const struct bpf_link_ops bpf_struct_ops_link_lops = {
348 .release = bpf_struct_ops_link_release,
349 .dealloc = bpf_struct_ops_link_dealloc,
350};
351
352int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
353 struct bpf_tramp_link *link,
354 const struct btf_func_model *model,
355 void *stub_func, void *image, void *image_end)
356{
357 u32 flags = BPF_TRAMP_F_INDIRECT;
358 int size;
359
360 tlinks[BPF_TRAMP_FENTRY].links[0] = link;
361 tlinks[BPF_TRAMP_FENTRY].nr_links = 1;
362
363 if (model->ret_size > 0)
364 flags |= BPF_TRAMP_F_RET_FENTRY_RET;
365
366 size = arch_bpf_trampoline_size(model, flags, tlinks, NULL);
367 if (size < 0)
368 return size;
369 if (size > (unsigned long)image_end - (unsigned long)image)
370 return -E2BIG;
371 return arch_prepare_bpf_trampoline(NULL, image, image_end,
372 model, flags, tlinks, stub_func);
373}
374
375static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
376 void *value, u64 flags)
377{
378 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
379 const struct bpf_struct_ops *st_ops = st_map->st_ops;
380 struct bpf_struct_ops_value *uvalue, *kvalue;
381 const struct btf_member *member;
382 const struct btf_type *t = st_ops->type;
383 struct bpf_tramp_links *tlinks;
384 void *udata, *kdata;
385 int prog_fd, err;
386 void *image, *image_end;
387 u32 i;
388
389 if (flags)
390 return -EINVAL;
391
392 if (*(u32 *)key != 0)
393 return -E2BIG;
394
395 err = check_zero_holes(st_ops->value_type, value);
396 if (err)
397 return err;
398
399 uvalue = value;
400 err = check_zero_holes(t, uvalue->data);
401 if (err)
402 return err;
403
404 if (uvalue->state || refcount_read(&uvalue->refcnt))
405 return -EINVAL;
406
407 tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
408 if (!tlinks)
409 return -ENOMEM;
410
411 uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
412 kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
413
414 mutex_lock(&st_map->lock);
415
416 if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
417 err = -EBUSY;
418 goto unlock;
419 }
420
421 memcpy(uvalue, value, map->value_size);
422
423 udata = &uvalue->data;
424 kdata = &kvalue->data;
425 image = st_map->image;
426 image_end = st_map->image + PAGE_SIZE;
427
428 for_each_member(i, t, member) {
429 const struct btf_type *mtype, *ptype;
430 struct bpf_prog *prog;
431 struct bpf_tramp_link *link;
432 u32 moff;
433
434 moff = __btf_member_bit_offset(t, member) / 8;
435 ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
436 if (ptype == module_type) {
437 if (*(void **)(udata + moff))
438 goto reset_unlock;
439 *(void **)(kdata + moff) = BPF_MODULE_OWNER;
440 continue;
441 }
442
443 err = st_ops->init_member(t, member, kdata, udata);
444 if (err < 0)
445 goto reset_unlock;
446
447 /* The ->init_member() has handled this member */
448 if (err > 0)
449 continue;
450
451 /* If st_ops->init_member does not handle it,
452 * we will only handle func ptrs and zero-ed members
453 * here. Reject everything else.
454 */
455
456 /* All non func ptr member must be 0 */
457 if (!ptype || !btf_type_is_func_proto(ptype)) {
458 u32 msize;
459
460 mtype = btf_type_by_id(btf_vmlinux, member->type);
461 mtype = btf_resolve_size(btf_vmlinux, mtype, &msize);
462 if (IS_ERR(mtype)) {
463 err = PTR_ERR(mtype);
464 goto reset_unlock;
465 }
466
467 if (memchr_inv(udata + moff, 0, msize)) {
468 err = -EINVAL;
469 goto reset_unlock;
470 }
471
472 continue;
473 }
474
475 prog_fd = (int)(*(unsigned long *)(udata + moff));
476 /* Similar check as the attr->attach_prog_fd */
477 if (!prog_fd)
478 continue;
479
480 prog = bpf_prog_get(prog_fd);
481 if (IS_ERR(prog)) {
482 err = PTR_ERR(prog);
483 goto reset_unlock;
484 }
485
486 if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
487 prog->aux->attach_btf_id != st_ops->type_id ||
488 prog->expected_attach_type != i) {
489 bpf_prog_put(prog);
490 err = -EINVAL;
491 goto reset_unlock;
492 }
493
494 link = kzalloc(sizeof(*link), GFP_USER);
495 if (!link) {
496 bpf_prog_put(prog);
497 err = -ENOMEM;
498 goto reset_unlock;
499 }
500 bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS,
501 &bpf_struct_ops_link_lops, prog);
502 st_map->links[i] = &link->link;
503
504 err = bpf_struct_ops_prepare_trampoline(tlinks, link,
505 &st_ops->func_models[i],
506 *(void **)(st_ops->cfi_stubs + moff),
507 image, image_end);
508 if (err < 0)
509 goto reset_unlock;
510
511 *(void **)(kdata + moff) = image + cfi_get_offset();
512 image += err;
513
514 /* put prog_id to udata */
515 *(unsigned long *)(udata + moff) = prog->aux->id;
516 }
517
518 if (st_map->map.map_flags & BPF_F_LINK) {
519 err = 0;
520 if (st_ops->validate) {
521 err = st_ops->validate(kdata);
522 if (err)
523 goto reset_unlock;
524 }
525 arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
526 /* Let bpf_link handle registration & unregistration.
527 *
528 * Pair with smp_load_acquire() during lookup_elem().
529 */
530 smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_READY);
531 goto unlock;
532 }
533
534 arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
535 err = st_ops->reg(kdata);
536 if (likely(!err)) {
537 /* This refcnt increment on the map here after
538 * 'st_ops->reg()' is secure since the state of the
539 * map must be set to INIT at this moment, and thus
540 * bpf_struct_ops_map_delete_elem() can't unregister
541 * or transition it to TOBEFREE concurrently.
542 */
543 bpf_map_inc(map);
544 /* Pair with smp_load_acquire() during lookup_elem().
545 * It ensures the above udata updates (e.g. prog->aux->id)
546 * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
547 */
548 smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
549 goto unlock;
550 }
551
552 /* Error during st_ops->reg(). Can happen if this struct_ops needs to be
553 * verified as a whole, after all init_member() calls. Can also happen if
554 * there was a race in registering the struct_ops (under the same name) to
555 * a sub-system through different struct_ops's maps.
556 */
557 arch_unprotect_bpf_trampoline(st_map->image, PAGE_SIZE);
558
559reset_unlock:
560 bpf_struct_ops_map_put_progs(st_map);
561 memset(uvalue, 0, map->value_size);
562 memset(kvalue, 0, map->value_size);
563unlock:
564 kfree(tlinks);
565 mutex_unlock(&st_map->lock);
566 return err;
567}
568
569static long bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
570{
571 enum bpf_struct_ops_state prev_state;
572 struct bpf_struct_ops_map *st_map;
573
574 st_map = (struct bpf_struct_ops_map *)map;
575 if (st_map->map.map_flags & BPF_F_LINK)
576 return -EOPNOTSUPP;
577
578 prev_state = cmpxchg(&st_map->kvalue.state,
579 BPF_STRUCT_OPS_STATE_INUSE,
580 BPF_STRUCT_OPS_STATE_TOBEFREE);
581 switch (prev_state) {
582 case BPF_STRUCT_OPS_STATE_INUSE:
583 st_map->st_ops->unreg(&st_map->kvalue.data);
584 bpf_map_put(map);
585 return 0;
586 case BPF_STRUCT_OPS_STATE_TOBEFREE:
587 return -EINPROGRESS;
588 case BPF_STRUCT_OPS_STATE_INIT:
589 return -ENOENT;
590 default:
591 WARN_ON_ONCE(1);
592 /* Should never happen. Treat it as not found. */
593 return -ENOENT;
594 }
595}
596
597static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
598 struct seq_file *m)
599{
600 void *value;
601 int err;
602
603 value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
604 if (!value)
605 return;
606
607 err = bpf_struct_ops_map_sys_lookup_elem(map, key, value);
608 if (!err) {
609 btf_type_seq_show(btf_vmlinux, map->btf_vmlinux_value_type_id,
610 value, m);
611 seq_puts(m, "\n");
612 }
613
614 kfree(value);
615}
616
617static void __bpf_struct_ops_map_free(struct bpf_map *map)
618{
619 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
620
621 if (st_map->links)
622 bpf_struct_ops_map_put_progs(st_map);
623 bpf_map_area_free(st_map->links);
624 if (st_map->image) {
625 arch_free_bpf_trampoline(st_map->image, PAGE_SIZE);
626 bpf_jit_uncharge_modmem(PAGE_SIZE);
627 }
628 bpf_map_area_free(st_map->uvalue);
629 bpf_map_area_free(st_map);
630}
631
632static void bpf_struct_ops_map_free(struct bpf_map *map)
633{
634 /* The struct_ops's function may switch to another struct_ops.
635 *
636 * For example, bpf_tcp_cc_x->init() may switch to
637 * another tcp_cc_y by calling
638 * setsockopt(TCP_CONGESTION, "tcp_cc_y").
639 * During the switch, bpf_struct_ops_put(tcp_cc_x) is called
640 * and its refcount may reach 0 which then free its
641 * trampoline image while tcp_cc_x is still running.
642 *
643 * A vanilla rcu gp is to wait for all bpf-tcp-cc prog
644 * to finish. bpf-tcp-cc prog is non sleepable.
645 * A rcu_tasks gp is to wait for the last few insn
646 * in the tramopline image to finish before releasing
647 * the trampoline image.
648 */
649 synchronize_rcu_mult(call_rcu, call_rcu_tasks);
650
651 __bpf_struct_ops_map_free(map);
652}
653
654static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
655{
656 if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
657 (attr->map_flags & ~BPF_F_LINK) || !attr->btf_vmlinux_value_type_id)
658 return -EINVAL;
659 return 0;
660}
661
662static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
663{
664 const struct bpf_struct_ops *st_ops;
665 size_t st_map_size;
666 struct bpf_struct_ops_map *st_map;
667 const struct btf_type *t, *vt;
668 struct bpf_map *map;
669 int ret;
670
671 st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
672 if (!st_ops)
673 return ERR_PTR(-ENOTSUPP);
674
675 vt = st_ops->value_type;
676 if (attr->value_size != vt->size)
677 return ERR_PTR(-EINVAL);
678
679 t = st_ops->type;
680
681 st_map_size = sizeof(*st_map) +
682 /* kvalue stores the
683 * struct bpf_struct_ops_tcp_congestions_ops
684 */
685 (vt->size - sizeof(struct bpf_struct_ops_value));
686
687 st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
688 if (!st_map)
689 return ERR_PTR(-ENOMEM);
690
691 st_map->st_ops = st_ops;
692 map = &st_map->map;
693
694 ret = bpf_jit_charge_modmem(PAGE_SIZE);
695 if (ret) {
696 __bpf_struct_ops_map_free(map);
697 return ERR_PTR(ret);
698 }
699
700 st_map->image = arch_alloc_bpf_trampoline(PAGE_SIZE);
701 if (!st_map->image) {
702 /* __bpf_struct_ops_map_free() uses st_map->image as flag
703 * for "charged or not". In this case, we need to unchange
704 * here.
705 */
706 bpf_jit_uncharge_modmem(PAGE_SIZE);
707 __bpf_struct_ops_map_free(map);
708 return ERR_PTR(-ENOMEM);
709 }
710 st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
711 st_map->links =
712 bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_links *),
713 NUMA_NO_NODE);
714 if (!st_map->uvalue || !st_map->links) {
715 __bpf_struct_ops_map_free(map);
716 return ERR_PTR(-ENOMEM);
717 }
718
719 mutex_init(&st_map->lock);
720 bpf_map_init_from_attr(map, attr);
721
722 return map;
723}
724
725static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
726{
727 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
728 const struct bpf_struct_ops *st_ops = st_map->st_ops;
729 const struct btf_type *vt = st_ops->value_type;
730 u64 usage;
731
732 usage = sizeof(*st_map) +
733 vt->size - sizeof(struct bpf_struct_ops_value);
734 usage += vt->size;
735 usage += btf_type_vlen(vt) * sizeof(struct bpf_links *);
736 usage += PAGE_SIZE;
737 return usage;
738}
739
740BTF_ID_LIST_SINGLE(bpf_struct_ops_map_btf_ids, struct, bpf_struct_ops_map)
741const struct bpf_map_ops bpf_struct_ops_map_ops = {
742 .map_alloc_check = bpf_struct_ops_map_alloc_check,
743 .map_alloc = bpf_struct_ops_map_alloc,
744 .map_free = bpf_struct_ops_map_free,
745 .map_get_next_key = bpf_struct_ops_map_get_next_key,
746 .map_lookup_elem = bpf_struct_ops_map_lookup_elem,
747 .map_delete_elem = bpf_struct_ops_map_delete_elem,
748 .map_update_elem = bpf_struct_ops_map_update_elem,
749 .map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
750 .map_mem_usage = bpf_struct_ops_map_mem_usage,
751 .map_btf_id = &bpf_struct_ops_map_btf_ids[0],
752};
753
754/* "const void *" because some subsystem is
755 * passing a const (e.g. const struct tcp_congestion_ops *)
756 */
757bool bpf_struct_ops_get(const void *kdata)
758{
759 struct bpf_struct_ops_value *kvalue;
760 struct bpf_struct_ops_map *st_map;
761 struct bpf_map *map;
762
763 kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
764 st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
765
766 map = __bpf_map_inc_not_zero(&st_map->map, false);
767 return !IS_ERR(map);
768}
769
770void bpf_struct_ops_put(const void *kdata)
771{
772 struct bpf_struct_ops_value *kvalue;
773 struct bpf_struct_ops_map *st_map;
774
775 kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
776 st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
777
778 bpf_map_put(&st_map->map);
779}
780
781static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
782{
783 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
784
785 return map->map_type == BPF_MAP_TYPE_STRUCT_OPS &&
786 map->map_flags & BPF_F_LINK &&
787 /* Pair with smp_store_release() during map_update */
788 smp_load_acquire(&st_map->kvalue.state) == BPF_STRUCT_OPS_STATE_READY;
789}
790
791static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
792{
793 struct bpf_struct_ops_link *st_link;
794 struct bpf_struct_ops_map *st_map;
795
796 st_link = container_of(link, struct bpf_struct_ops_link, link);
797 st_map = (struct bpf_struct_ops_map *)
798 rcu_dereference_protected(st_link->map, true);
799 if (st_map) {
800 /* st_link->map can be NULL if
801 * bpf_struct_ops_link_create() fails to register.
802 */
803 st_map->st_ops->unreg(&st_map->kvalue.data);
804 bpf_map_put(&st_map->map);
805 }
806 kfree(st_link);
807}
808
809static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
810 struct seq_file *seq)
811{
812 struct bpf_struct_ops_link *st_link;
813 struct bpf_map *map;
814
815 st_link = container_of(link, struct bpf_struct_ops_link, link);
816 rcu_read_lock();
817 map = rcu_dereference(st_link->map);
818 seq_printf(seq, "map_id:\t%d\n", map->id);
819 rcu_read_unlock();
820}
821
822static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
823 struct bpf_link_info *info)
824{
825 struct bpf_struct_ops_link *st_link;
826 struct bpf_map *map;
827
828 st_link = container_of(link, struct bpf_struct_ops_link, link);
829 rcu_read_lock();
830 map = rcu_dereference(st_link->map);
831 info->struct_ops.map_id = map->id;
832 rcu_read_unlock();
833 return 0;
834}
835
836static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
837 struct bpf_map *expected_old_map)
838{
839 struct bpf_struct_ops_map *st_map, *old_st_map;
840 struct bpf_map *old_map;
841 struct bpf_struct_ops_link *st_link;
842 int err;
843
844 st_link = container_of(link, struct bpf_struct_ops_link, link);
845 st_map = container_of(new_map, struct bpf_struct_ops_map, map);
846
847 if (!bpf_struct_ops_valid_to_reg(new_map))
848 return -EINVAL;
849
850 if (!st_map->st_ops->update)
851 return -EOPNOTSUPP;
852
853 mutex_lock(&update_mutex);
854
855 old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
856 if (expected_old_map && old_map != expected_old_map) {
857 err = -EPERM;
858 goto err_out;
859 }
860
861 old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
862 /* The new and old struct_ops must be the same type. */
863 if (st_map->st_ops != old_st_map->st_ops) {
864 err = -EINVAL;
865 goto err_out;
866 }
867
868 err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data);
869 if (err)
870 goto err_out;
871
872 bpf_map_inc(new_map);
873 rcu_assign_pointer(st_link->map, new_map);
874 bpf_map_put(old_map);
875
876err_out:
877 mutex_unlock(&update_mutex);
878
879 return err;
880}
881
882static const struct bpf_link_ops bpf_struct_ops_map_lops = {
883 .dealloc = bpf_struct_ops_map_link_dealloc,
884 .show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
885 .fill_link_info = bpf_struct_ops_map_link_fill_link_info,
886 .update_map = bpf_struct_ops_map_link_update,
887};
888
889int bpf_struct_ops_link_create(union bpf_attr *attr)
890{
891 struct bpf_struct_ops_link *link = NULL;
892 struct bpf_link_primer link_primer;
893 struct bpf_struct_ops_map *st_map;
894 struct bpf_map *map;
895 int err;
896
897 map = bpf_map_get(attr->link_create.map_fd);
898 if (IS_ERR(map))
899 return PTR_ERR(map);
900
901 st_map = (struct bpf_struct_ops_map *)map;
902
903 if (!bpf_struct_ops_valid_to_reg(map)) {
904 err = -EINVAL;
905 goto err_out;
906 }
907
908 link = kzalloc(sizeof(*link), GFP_USER);
909 if (!link) {
910 err = -ENOMEM;
911 goto err_out;
912 }
913 bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
914
915 err = bpf_link_prime(&link->link, &link_primer);
916 if (err)
917 goto err_out;
918
919 err = st_map->st_ops->reg(st_map->kvalue.data);
920 if (err) {
921 bpf_link_cleanup(&link_primer);
922 link = NULL;
923 goto err_out;
924 }
925 RCU_INIT_POINTER(link->map, map);
926
927 return bpf_link_settle(&link_primer);
928
929err_out:
930 bpf_map_put(map);
931 kfree(link);
932 return err;
933}